This invention involves sorption apparatus and its method of use. The basic thermodynamic principles of sorption units have been known since the last century and have developed from very simple periodically operating refrigerators to the continuously operating absorber-type refrigerators. The recovery of fluorinated hydrocarbons and the resulting progress in compressor technology produced compression-type refrigeration machines after World War II. This completely replaced the periodically operating refrigeration machines and left only a few fields of application for the continuously operating refrigeration machines, i.e. camping refrigerators or cold water coolers. The increasing energy cost resulting from the 1973/1974 energy crisis led to the installation of compression-type refrigeration machines with electric drives for heating systems, similar to the househould-refrigerator type. Since the total efficiency of such heating systems including the efficiency rate of power plants, is higher only in individual cases compared with the efficiency of updated modern conventional heating systems, the idea of continuously operating sorption units with direct primary energy supply (fuel oil, fuel gas, coal) was again utilized. The advantage of continuously operating sorption units lies in the increase of the total performance figure and efficiency which can be reached by eliminating the energy losses of power plants.
Since both systems, the compression-type refrigeration machine and the continuously operating sorption unit, are initially designed for continuous refrigeration, they prove to be unsatisfactory in many respects for use in heating systems.
The basic difference between heat pumps and refrigeration machines is in their field of application. Refrigeration machines are designed for a continous chilling operation at an almost constant cooling level. Since recycling of the waste heat from these types of machines was only planned in exceptional cases, its quantity and temperature were not of interest. This is quite different with heat pumps where the waste heat becomes "useful" heat. At low ambient temperatures, this useful heat should be available at a higher output temperature and in higher quantities. But under those conditions, the temperature of the heat source, which was the chilling temperature for refrigeration machines, is especially low. Therefore, this means that there is a large difference between effective temperature and heat source temperature, when the demand for useful heat is high. In addition, both temperatures are independent of each other and subject to extreme fluctuations not only because of changing weather conditions but also because of consumer behavior. Therefore, generally when there is sufficient heat available from the heat source there is no demand for it and when the heat source is exhausted of available heat it is during a period of increased heat demand. Under these operating conditions, there will be a drastic drop in the performance figures of continuously operating apparatus. The result is a reduced effective heat generation which must be compensated for either by installing additional heat storage capacity and/or switching over to an auxiliary heating system. Due to the low temperature of the heat sources and the continuing need for economic performance figures, the temperature of the useful heat in all present heat pump systems have been restricted to values below 60.degree. C. This restriction has required the installation of low-temperature heating systems, which is only economical in new buildings. This is only possible in exceptional cases in connection with old or reconstructed or renovated buildings.
All available commercial sorption heat pumps are continuously operating units filled with the toxic and inflammable material combination of ammonia/water. The maximum legal allowable ammonia concentration requires certain switching arrangements which are unfavorable for the performance of heat pumps. Other more harmless material combinations used in the sorption refrigeration technology have been found to be too inefficient for use in heat pumps. If one takes into account the high energy consumption for solvent pumps and their additional quite high susceptibility to wear, the performance figures than can be obtained with these machines according to their manufacturers are acceptable. However, during practical use, with low heat source temperatures, fluctuating heat demands or in case of periodic operation, these performance figures cannot be attained. In addition, this type of unit is designed for an average useful heat demand and an additional heat source must be provided for cases of increased heat demand. This produces a doubling of investment costs and floor space because the required auxiliary equipment must be designed for maximum heat demand.
For an optimum utilization of the heat offered by the heat source on one hand and satisfaction of the heat demand as well as during periods where primary energy is available at more economic rates on the other hand, German Pat. No. DE-OS 25 23 429 suggests to store the heat from the heat source in a special heat retaining mass and later on transfer it to a heat reservoir with the aid of a compressor-type heat pump with electric drive, taking advantage of the lower night-tariff rates. Generally, these proposals cannot always be realized. This is due to required large storage capacities and the low temperature of the useful heat together with the necessary temperature difference in the heat exchangers of the heat reservoir. Thus, an effective temperature spreading in the heat retaining mass is almost impossible.
One type of heat reservoir that has been functioning satisfactority for decades is the so-called "Nachtstromwarmespericher" (heat reservoir taking up electrical energy during the night-tariff periods) which is being heated up during the low-tariff periods in the night. Here a heat retaining mass is being heated up to more than 600.degree. C. during low-load/low-tariff periods. The required useful heat will then be taken from the specific heat of the heat-retaining mass during high-tariff periods (days). However, the necessary high storage temperatures will result in extensive heat losses despite thicker insulation layers. A heat pump effect is impossible.
European Pat. No. EP-OS 00 262 557 describes a periodically operating sorption-type heat reservoir with the objective to store the motive energy for the heat pump at sufficiently high temperatures. However, the design of this heat reservoir remains open and storage of heat coming from a heat source is not provided. For a "quasi-continuous operation" the abundant provision of two separate sorption storage units is required.
The objective of all known refrigeration machines is to keep the temperature in the chilling section constant without any external manipulations. But also for units which are designed for waste heat recycling from condensors or boiler absorbers, the cooling temperature controllers are designed for maximum refrigeration.
German Pat. No. DE-PS 596 308 describes a device for hot water preparation by condensation or else adsorption in a periodically operating adsorption-refrigeration unit. However, here the thermostat-controllers let warm water run off unused in order not to impair the chilling effect.